Clamp for a key cutting machine

ABSTRACT

Clamp for key cutting machines, of the type comprising a pair of jaws ( 6, 10 ) mounted on a single pin ( 2 ) fixed to the machine structure and associated with a knob ( 22 ) screwable on a threaded portion of said pin ( 2 ) and acting in the sense of causing said jaws to forcedly approach each other, against the elastic reaction of a spring ( 14 ) tending to repel them, and to retain a key positioned between them, characterised by comprising a friction type overload clutch ( 18, 20, 30 ) interposed between said knob ( 22 ) and said pin ( 2 ).

FIELD OF THE INVENTION

The present invention relates to an improved clamp for a key cuttingmachine.

BACKGROUND OF THE INVENTION

Key cutting machines, also commonly called duplicating machines, arewell known. A known type of such machines comprises a base on which afeeler is mounted to mechanically sense the notches of the notchingpattern of an original key to be duplicated, together with a millingcutter to form similar notches on a blank key to be cut.

On the same base a movable structure is also mounted supporting twoclamps, to which the original key to be duplicated and the blank key tobe cut are fixed. The arrangement of the parts is such that the two keysare disposed with the axes of their respective shanks parallel and thatwhen the original key faces the feeler the blank key faces the cutter.

In this manner, by moving the movable structure such that the feelerslides along the pattern notches of the original key the cutter forms,on the blank key, notches which are substantially identical to those ofthe original key in terms of position and depth.

In another known type of duplicating machine the movement of the blankkey to be cut relative to the cutter is obtained mechanically on thebasis of notching pattern data contained in a database. In this case,cutting the blank key does not require the physical presence of theoriginal key as the notching data can be read off at a prior moment by adevice separate from the duplicating machine, or can be made availablevia a previously memorized notching code.

In all cases the blank key to be cut must at least be retained by aclamp in a position in front of a milling cutter and is moved relativeto said cutter such that this forms in the key edge the notchescorresponding to the notching pattern to be provided.

Known clamps generally comprise two jaws, between which the keyconcerned is clamped. These jaws are mounted on a generally vertical pinand are maintained spaced apart by a spring. The pin has its upperportion threaded and on this a knob is screwed, which when operated bythe operator causes the two jaws to move towards each other and clampthe interposed key.

A drawback of known clamps of this type is that if the knob is tooloosely tightened the key does not become securely fixed and can vibrateduring milling, such that in some cases it can even become detached fromthe clamp. These is hence a risk of cutter breakage and in any event animperfect notching result. If instead the knob is too tightly tightened,the clamp can undergo early wear and the key be damaged, especially ifmade of soft material such as aluminium.

To illustrate, U.S. Pat. No. 4,709,511, granted Dec. 1, 1987, disclosesa clamp for duplicating machines for keys. The clamp includes avertically extending pin (4) with a threaded upper end, a pair of jaws(1, 2) mounted on the pin, and supported on a support carriage (3), asshown in FIG. 1. A spring (6,8) or other resilient member normallybiases, or spaces, the jaws apart so that a key may be positionedtherebetween. Rotation of a handgrip (10) about the threaded upper ofpin (4) overcomes the bias of the spring, and applies a clamping forceto the key to retain same in fixed position in the slot formed betweenthe jaws. A rib (12), or similar projection, is defined on the lowerjaw, to provide a lever-like force that prevents the jaws from stickingtogether during the clamping phase, and overcomes difficulties inopening the jaws during the release phase of the cycle of operation.

U.S. Pat. No. 6,641,339, granted Nov. 4, 2003, discloses another clampfor a key duplicating machine. The clamp includes a pair of jaws (10,12)mounted on a vertically extending pin (6); the jaws are supported bybase (2), which encircles the lower end of the pin. The jaws arenormally biased apart by a coil spring or other resilient member, sothat a key (14) may be inserted into the gap between the jaws. The jawsare mounted on the pin, and the upper end of the pin is threaded intoengagement with handgrip (16). The handgrip, or knob, is screwed intothe upper end of pin (6) to lock key (14), and jaws (10,12) to the base(2). A gauge (20) is operatively associated with the seat to define aproper position for the key.

The clamping force delivered to the jaws, to maintain the keys in fixedposition, was fixed in magnitude. The need for a force of variablemagnitude, within a clamp, to compensate for different keyconfigurations, and the diverse materials used in keys, includingreadily deformable aluminum and other soft metals or plastics incomposites thereof, remained unsatisfied. Such need is addressed by theinstant invention, wherein the inventor has provided a friction clutchinterconnected between the knob and the pin; the friction clutch ishoused within the interior of the knob.

BRIEF SUMMARY OF THE INVENTION

An object of the invention is to eliminate this drawback by making theoperation of fixing a key to the duplicating machine clamp independentof the operator's ability and experience.

This and further objects which will be apparent from the ensuingdescription are attained according to the invention by an improved clampfor key cutting machines as described in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention is further describedhereinafter with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a clamp according to the invention;

FIG. 2 shows the clamp in a front elevational view in the directionII-II of FIG. 3;

FIG. 3 is a vertical section therethrough on the line III-III of FIG. 2;and

FIG. 4 is a perspective view of applicant's clamp, with a dynamometricmechanism positioned between the knob and the pin of the clamp; theremainder of the clamp is shown in dotted outline.

DETAILED DESCRIPTION

As can be seen from the figures the clamp of the invention is applied tothe structure of a duplicating machine, not shown in the drawings. Itcomprises a vertical pin 2, which is fixed to said structure and towhich a base plate 4 is fixed, on which the square-based lower jaw 6 ofthe clamp rests.

A lever 8 is also applied to the base plate 4 and interacts with thefixed jaw 6 to enable the clamp to be positioned in four differentangular positions rotated through 90° to, in this manner arrange, theclamp for fixing keys of different profiles, in accordance withtraditional techniques which do not form an aspect of the presentinvention.

The clamp of the invention also comprises an upper jaw 10 which is alsosupported centrally by the pin 2 and together with the lower jaw definesfour slots 12 for housing and fixing keys of different profile.

Between the two jaws 6 and 10 a coil 14 spring is disposed, as shown inFIG. 3, acting to maintain the upper jaw 10 spaced from the lower jaw 6along the pin 2, thereby maintaining the four slots 12 open.

An exterior screw thread 15 is formed on the upper portion of the pin 2.An internally threaded sleeve 16 is screwed onto thread 15. The extentof screwing sleeve 16 onto the pin 2 urges the upper jaw 10, to agreater or lesser extent, towards the lower jaw 6 against the elasticreaction of the spring 14.

A first sleeve 18 is associated with cap 16, collar 18 is free to slideaxially along the cap, but is unable to rotate about it. The collar 18includes on its upper annular surface a gear teeth 19. Teeth 19 engagein the inclined gear teeth 21 of second sleeve 20, which is joined tooperating knob 22. This knob 22 is fixed to the upper threaded portionof the cap 16 by a nut 24 housed in a cavity 26 provided in the top ofthe knob 22 and closed by a plug 28.

A coil spring 30 interposed between the sleeve 18 and a lower flange 32of the cap 16 maintains the two frontal toothed portions of the sleeves18 and 20 elastically coupled together.

The clamp of the invention operates in the following manner.

During preliminary setting, the nut 24 is screwed down to a greater, orlesser, extent to load the spring 30 to the value required for thereaction torque of the dynamometric device. Such device comprises spring30, and the two sleeves 18, 20 with gear teeth 19, 21, respectively,which are maintained coupled together by the spring.

After the pair of jaws 6, 10, maintained spaced apart by the spring 14,have been positioned on the pin 2 such as to make operative the chosenslot 12 corresponding to the key to be clamped, the key is positioned inthe slot and the knob 22 operated. This action is transmitted, via thedynamometric device, to the cap 16, which is screwed onto threads 15 onthe pin 2 to cause the upper jaw 10 to approach the jaw 6, and henceclamp the key therebetween.

The intensity of this clamping is governed by the dynamic device. Morespecifically, after the upper jaw 10 has come into contact with the key,the reaction to further screwing of the cap 16 is controlled by thedynamic device. Until a certain value is obtained, the effect of thespring 30 prevails to maintain gear teeth 19 and 21 on sleeves 18, 20coupled together, whereas when this value is exceeded, the inclined gearteeth 19, 21 of the sleeves 18 and 20 slide over each other withoutcausing further rotation of the cap 16, and hence without providing afurther clamping effect on the key.

In practice the torque transmitted by the knob 22 to the cap 16 andhence the intensity of the clamping on the key is related to theinclination of the gear teeth 19, 21 of the sleeves 18 and 20, and tothe preload of the spring 30. The inclination of the teeth is evidentlyfixed, whereas the preload of the spring 30 can be adjusted by screwingthe nut 24 to a greater, or lesser extent, along the upper threadedportion of the cap 16.

From the aforegoing it is apparent that the improved clamp, according tothe invention is particularly advantageous compared with traditionalclamps for key cutting machines, in that it ensures a constant keyclamping force without the risk of damaging the key and/or the millingcutter, independently of the ability and experience of the operator.Moreover it enables the value of this constant clamping force to bepredefined, to adapt the clamp to the different possible key materials.

1. An improved clamp for key cutting machines, of the type comprising apair of jaws mounted on a single pin fixed to the machine structure andassociated with a knob screwable on a threaded portion of said pin andacting in the sense of causing said jaws to forcedly approach eachother, against the elastic reaction of a spring tending to repel them,and to retain a key positioned between them, comprising a dynamometricdevice interposed between said knob and said pin.
 2. The clamp asclaimed in claim 1, wherein said jaws are of square plan and are fixableto said pin in four positions angularly rotated through 90° to renderthe required pair of faces operative.
 3. The clamp as claimed in claim2, comprising lever means to lock the pair of jaws in the desiredannular position about said pin.
 4. The clamp as claimed in claim 1,wherein said pin comprises a threaded portion on which a sleeve isscrewable to act and rest on one of the two jaws, namely the jaw whichis movable along said pin, while the other jaw is axially fixed aboutsaid pin, said dynamometric device being interposed between said knoband said sleeve.
 5. The clamp as claimed in claim 4, wherein saiddynamometric device comprises a pair of sleeves rotatably rigid withsaid sleeve screwed onto said pin, and also with said knob, said sleevesof said dynamometric device being provided with toothed portionsmaintained coupled together by elastic means and becoming decoupled whena predetermined torque is exceeded, by the axial sliding of one of saidsleeves relative to the member with which it is torsionally rigid,against the elastic reaction of said elastic means.
 6. The clamp asclaimed in claim 5, wherein one sleeve is axially slidable along saidsleeve screwed to said pin, whereas the other sleeve is rigid with saidknob.
 7. The clamp as claimed in claim 6, wherein said elastic meansconsist of a coil spring interposed between said sleeve axially slidablealong said sleeve screwed to said pin, and an end flange provided inthis latter sleeve.
 8. The clamp as claimed in claim 6, wherein saidsleeve screwed to said pin is provided with a threaded portion on whicha nut can be screwed to fix said knob to said sleeve and to preload saidelastic means cooperating with said toothed sleeves.
 9. The clamp asclaimed in claim 8, wherein said preloading nut is housed in a cavityprovided in said knob and closable by a plug.
 10. A clamp adapted foruse with a key cutting machine, said clamp comprising: a) a verticallyextending pin having an upper end and a lower end and an elongatedshank, extending between said upper and lower ends, b) the lower end ofsaid pin adapted to be secured to a key cutting machine, c) a lower jawincluding a central aperture that fits over said shank so that saidlower jaw rests upon a base plate, d) an upper jaw including a centralaperture that fits over said shank so that said upper jaw is locatedabove said lower jaw, e) a plurality of slots defined between said upperand lower jaws, f) first resilient means located around said pin andbetween said upper and lower jaws to normally bias the jaws apart andmaintain the slots in opened condition, g) the exterior of said upperend of said shank of said pin being threaded, h) an internally threadedcap screwed onto the upper end of said shank, i) a flange defined at thelower end of said cap, j) a first sleeve that slides axially along theexterior of said cap, k) a plurality of teeth located on the uppersurface of said first sleeve, l) a second sleeve located above saidfirst sleeve on said post, m) a plurality of teeth located on saidsecond sleeve facing said plurality of teeth on said first sleeve, n)second resilient means disposed about said cap to urge said teeth onsaid first and said teeth on said second sleeves into engagement, o) adownwardly opening knob that fits over said shank of said pin, saidfirst and said second sleeves, said cap, and said second resilientmeans, p) a nut secured to the upper threaded end of said cap to joinsaid knob to said cap, q) the invention being characterized by anoverload clutch interposed between said knob and said pin, r) saidoverload clutch comprising: (1) at least one gear tooth located on theupper surface of said first sleeve, (2) at least one gear tooth locatedon the lower surface of said second sleeve facing said tooth on saidfirst sleeve, and (3) a spring disposed about said cap to bias the teethon said first and second teeth into engagement, s) said nut beingadjusted along the upper end of said cap to vary the pre-load on saidspring, t) whereby the rotation of said knob transmits a clamping forceto said upper jaw to maintain contact with a key retained in one of saidslots until the pre-set value imparted by said spring is exceeded, andsaid teeth on said sleeves slide over each other.